The present invention relates to compressors, and more specifically to refrigerant compressors.
In conventional practice, refrigerant circuits include a refrigerant compressor. The cooling potential of the refrigeration circuit is at least partially determined by the suction pressure of the compressor, and the pressure discharged from the compressor is at least partially determined by the capacity of the compressor. In general, a larger compressor capacity will lead to a larger cooling potential of the refrigerant circuit.
Currently, a common way to adjust the cooling potential of a refrigerant circuit is to constrict flow through the suction port, thus decreasing the pressure present in the suction port. This process is known to those skilled in the art as suction pressure throttling and is accomplished by positioning a throttling valve before the suction port. The throttling valve reduces the mass flow entering the compressor and therefore lowers the cooling potential of the refrigerant circuit. This type of control is often employed with a variable throttling valve that allows control of the degree of throttling and thus variably controls the cooling potential of the system. This in turn allows control of the temperature of a temperature controlled space.
Conventional arrangements, such as ones incorporating suction pressure throttling, have many disadvantages including a lack of accurate temperature control in the frozen temperature range, and problems inherent with suction pressure throttling. One problem is potentially high pressure ratios resulting from very low suction port pressures, potentially causing damage to the compressor.